The invention relates to a switching device for light beams, comprising a switching member with at least one row of windows. Each window consists of a block of electro-optical material which is connected to a first surface of a rigid carrier and which is formed with two oppositely situated, parallel, light-transmissive principal surfaces and two side surfaces which are also oppositely situated and which extend between the principal surfaces. Across each side surface is an electrode which is conductively connected to a conductor.
A device of this kind is known from U.S. Pat. No. 3,873,187. The known device comprises a switching member in the form of a rigid carrier, for example, a glass plate on which there are provided blocks of electro-optical material, for example, PLZT. The space between each pair of adjacently situated blocks is filled with conductive material in which a thin wire conductor is embedded. This conductive material together with its associated wire conductor forms an electrode on each of the side surfaces of the blocks facing the space. When a potential difference is applied between the electrodes on opposite sides of a block, the intermediate electro-optical material becomes double-refractive. When the switching member is arranged between a polarizer and an analyzer, the intensity of a light beam passing through a block can be varied by varying the potential difference between the associated electrodes, so that a switching device for light beams is provided. Switching devices of this kind can be used, for example, in devices for reading or printing documents, such as transmitters and receivers of facsimile systems.
Electrodes of adjacently situated blocks are connected to a common conductor in the switching member of the known switching device, so that a signal applied to a block could influence an adjacent block. Moreover, the electro-optical material generally also has piezo-electric properties so that when a potential difference is applied between the electrodes, the material tends to contract or expand, thus causing stresses in the carrier which have an unintended effect, via the carrier, on the double refraction in other blocks.